Vapor nucleation method

Abstract

A metal processing furnace of the indirect arc type employing opposed electrodes projected into an ionizable atmosphere is provided with novel filter-like, vapor nucleation means which enables the furnace to be utilized for numerous different metal melting/smelting operations in a manner which precludes the presence of metals and metal oxides in their vapor or particle forms in process effluent gases delivered from the furnace. The furance achieves substantial operating advantages in the manufacture of ferroalloys, silicon and beryllium-copper metals, and comparable products including carbides such as silicon carbide.

I claim: 
     
       1. In a method of processing a metal values charge material in a furnace shell at a temperature which produces vapors from the group comprised of metal vapors and metal oxide vapors, the steps of: (a) developing an ionized atmosphere within said furnace shell to a temperature producing vapors from the group comprised of metal vapors and metal oxide vapors of said metal values charge;   (b) introducing said metal values charge material into said ionized atmosphere by gravity flow and thermally processing said introduced metal values charge material into a metal values phase and a non-metallic gaseous phase;   (c) flowing said non-metallic gaseous phase through a nucleation filter within said furnace shell that separates vapors from the group consisting of metal vapors and metal oxide vapors of said metal values charge material from said non-metallic gaseous phase for return to said ionized atmosphere;   (d) collecting said metal values phase beneath said ionized atmosphere for subsequent removal from within said furnace shell; and   (e) emitting portions of said non-metallic gaseous phase passed through said nucleation filter from within said furnace shell in a condition free of metal and metal oxide constituents from said metal values charge material; said nucleation filter being porous, non-graphitic carbon.     
     
     
       2. The invention defined by claim 1 wherein said nucleation filter porous, non-graphitic carbon has an ash impurity content. 
     
     
       3. The invention defined by claim 1 wherein said metal values charge material consists of a mixture of metal oxides and an oxide reductant containing carbon, said metal oxides including iron oxide and a metal oxide from the group consisting of the oxides of chromium, silicon, and magnesium, and said collected metal values phase being from the group comprised of ferrosilicon, ferrochrome, ferrosilicochrome, and ferrosilicomagnesium. 
     
     
       4. The invention defined by claim 1 wherein said metal values charge material is comprised of silica and carbon, said collected metal values phase being silicon carbide.